COMBUSTION OF CARBONACEOUS MATERIALS BY CU-K-V BASED CATALYSTS .2. REACTION-MECHANISM

In Part I the chemical and microstructural nature of Cu-K-V catalysts for diesel soot combustion was assessed. In this second communication the reaction mechanism of these catalysts is studied by testing their activity through either differential scanning calorimetry (DSC) or tem perature-programmed oxidation (TPO), performed on catalyst-carbon mixt ures. The following parameters were varied: the particle size of both the catalyst and the carbon powders, the catalyst-to-carbon weight rat io, the catalyst composition (besides the standard Cu-K-V catalyst def ined in Part I, binary catalysts based on a single copper or potassium vanadate + KCl were also considered). On the basis of the obtained re sults the presence of liquid eutectic phases (whose formation was dete cted via DSC runs performed in the absence of carbon) is found to be a key factor in determining the catalytic activity of all tested cataly sts since it dramatically improves the catalyst-carbon contact. Once l iquid phases are formed at suitable temperatures (ranging from 330 to 480 degrees C depending on the catalyst nature), the catalytic combust ion likely proceeds according to redox mechanisms.